Hemophilus Infections Health Article

Definition

Hemophilus infections, most of which are due to Haemophilus influenzae infections, are a group of contagious diseases that are caused by a bacterium and affect only humans. Some hemophilus infections are potentially fatal.

Description

H. influenzae is a common organism worldwide; it has been found in the nasal secretions of as many as 90 percent of healthy individuals in the general population. Hemophilus infections are characterized by acute inflammation with a discharge (exudate). They may affect almost any organ system but are most common in the respiratory tract. The organism can be transmitted by person-to-person contact or by contact with nasal discharges and other body fluids. Hemophilus infections in the United States are most likely to spread in the late winter or early spring.

Demographics

The primary factor influencing the rate of infection is age; children between the ages of six months and four years are most vulnerable to H. influenzae. In the twentieth century, about 50 percent of children would acquire a hemophilus infection before reaching one year of age; almost all children would develop one before age three. In the United States, these figures have declined, however, as a result of the increasing use of hemophilus vaccines for children. Worldwide, however, Haemophilus influenzae remains a significant childhood pathogen. It is the primary cause of childhood meningitis and the second most common cause of childhood pneumonia. In developing countries, Haemophilus influenzae is responsible for 500,000 annual deaths in children under the age of five.

Causes and symptoms

Hemophilus infections are primarily caused by Haemophilus influenzae, a bacterium that is capable of spreading from the nasal tissues and upper airway, where it is usually found, to the chest, throat, or middle ear. The organism sometimes invades localized areas of tissue, producing meningitis, infectious arthritis, conjunctivitis, cellulitis, epiglottitis, or inflammation of the membrane surrounding the heart. The most serious infections are caused by a strain called H. influenzae b (Hib). Before routine vaccination, Hib was the most common cause of bacterial meningitis and responsible for most of the cases of acquired mental retardation in the United States.

Bacterial sepsis in the newborn

Bacterial sepsis (the presence of illness-causing microorganisms, or their poisons, in the blood) is a potentially fatal illness in newborn infants. The child may acquire the disease organism as it passes through the mother's birth canal or from the hospital environment. H. influenzae can also produce inflammations of the eye (conjunctivitis) in newborn children. The signs of sepsis may include fever, fussiness, feeding problems, breathing difficulties, pale or mottled skin, or drowsiness. Premature birth is the most significant risk factor for hemophilus infections in newborns.

Epiglottitis

Epiglottitis is a potentially fatal hemophilus infection. Although children are more likely to develop epiglottitis, it can occur in adults as well. When the epiglottis (the flap that covers the trachea during swallowing so that food odes not enter the lungs) is infected, it can swell to the point where it blocks the windpipe. The symptoms of epiglottitis include a sudden high fever, drooling, the feeling of an object stuck in the throat, and stridor (a high-pitched, noisy respiratory sound). The epiglottis will look swollen and bright red if the doctor examines the patient's throat with a laryngoscope (a viewing device).

Meningitis

Meningitis caused by Hib is most common in children between nine months and four years of age. The child usually develops upper respiratory symptoms followed by fever, loss of appetite, vomiting, headache, and a stiff or sore neck or back. In severe cases, the child may have convulsions or go into shock or coma.

Other infections

Hib is the second most common cause of middle ear infection and sinusitis in children. The symptoms of sinusitis include fever, pain, bad breath, and coughing. Children may also develop infectious arthritis from Hib. The joints most frequently affected are the large weight-bearing ones.

Diagnosis

The diagnosis is usually based on a combination of the patient's symptoms and the results of blood counts, cultures, or antigen detection tests.

Laboratory tests

Laboratory tests can be used to confirm the diagnosis of hemophilus infections. The bacterium can be grown on chocolate agar or identified by blood cultures or Gram stain of body fluids. Antigen detection tests can be used to identify hemophilus infections in children. These tests include latex agglutination and electrophoresis.

Other laboratory findings that are associated with hemophilus infections include anemia (low red blood cell count) and a drop in the number of white blood cells in children with severe infections. Adults often show an abnormally high level of white blood cells; cell counts of 15,000 to 30,000/mm³ are not unusual.

Treatment

Because some hemophilus infections are potentially fatal, treatment is started without waiting for the results of laboratory tests.